Electrolyte and sodium ion battery

Abstract

The invention relates to the technical field of sodium ion batteries, in particular to an electrolyte and a sodium ion battery. The electrolyte comprises an organic solvent, a sodium salt and an additive, the additive comprises at least one of compounds with the structure shown in the specification; in the formula # imgabs0, R is selected from at least one of hydrogen, halogen, silyl, substituted or unsubstituted C1-C6 alkyl, phenyl, substituted phenyl, amido, pyrrolyl, thienyl, furyl, pyridyl, pyrazinyl and pyrimidyl. According to the electrolyte disclosed by the invention, by adding the additive containing fluorine and silicon, the problems of transition metal dissolution and electrode corrosion caused by HF are effectively solved, and construction of a complete, compact, high-stability and rigid-flexible positive solid electrolyte membrane is realized; therefore, the cycle performance of the sodium-ion battery is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion batteries, and in particular to an electrolyte and a sodium ion battery. Background Art

[0002] With the rapid development and growth of portable electronic devices and new energy vehicles, lithium-ion batteries have been widely used. However, the limited lithium reserves in the earth's crust greatly restrict its further large-scale application. Sodium and lithium have similar chemical properties, and sodium resources are abundant and cheap, so sodium-ion batteries are ideal large-scale energy storage systems. However, sodium-ion batteries have poor cycle performance, especially when used in high temperature and high voltage environments, which restricts their widespread application.

[0003] The electrolyte of sodium-ion batteries contains a certain amount of H2O, which will react with the sodium salt in the electrolyte to generate HF. HF will corrode the positive electrode and cause the dissolution of transition metal ions, resulting in loss of active substances, causing the battery's capacity to decay and cycle performance to deteriorate. In addition, the commonly used sodium-ion battery electrolyte is easily oxidized and decomposed under high temperature and high voltage, and the cathode electrolyte interface (CEI) formed is unstable, the battery's coulombic efficiency is reduced, and the capacity decays rapidly.

[0004] Electrolyte additives are an effective way to improve the electrochemical performance of electrode materials and have high economic feasibility. Therefore, it is necessary to develop a sodium ion battery electrolyte additive that can eliminate trace water and HF in the electrolyte in a high temperature and high voltage environment and form a stable CEI film, effectively improving the electrochemical performance of sodium ion batteries.

[0005] In view of this, this invention is proposed. Summary of the invention

[0006] The first object of the present invention is to provide an electrolyte which effectively solves the problem of transition metal dissolution and electrode corrosion caused by HF by adding fluorine- and silicon-containing additives, and can form a stable CEI film with high mechanical strength on the surface of the positive electrode.

[0007] The second object of the present invention is to provide a sodium ion battery, which improves the cycle performance of the sodium ion battery, especially the cycle performance under high temperature and high pressure conditions.

[0008] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0009] In a first aspect, the present invention provides an electrolyte solution, comprising an organic solvent, a sodium salt and an additive; the additive comprises at least one of the compounds having the structure shown below;

[0010] In the formula, R is selected from at least one of hydrogen, halogen, silane, substituted or unsubstituted C1-C6 alkyl, phenyl, substituted phenyl, amine, pyrrolyl, thienyl, furanyl, pyridyl, pyrazinyl and pyrimidyl.

[0011] Furthermore, the additive includes at least one of the compounds having structures shown in formula (I) to formula (VII);

[0012]

[0013]

[0014] Furthermore, the mass of the additive accounts for 0.001% to 10% of the total mass of the electrolyte.

[0015] Further, the sodium salt includes at least one of sodium hexafluorophosphate, sodium perchlorate, sodium hexafluoroarsenate, sodium p-toluenesulfonate, sodium tetrafluoroborate, sodium bis(trifluoromethylsulfonyl)imide and sodium bis(perfluoroethylsulfonyl)imide.

[0016] Furthermore, in the electrolyte, the concentration of the sodium salt is 0.5 to 3 mol / L.

[0017] Furthermore, the organic solvent includes at least one of a linear carbonate solvent, a cyclic carbonate solvent and a carboxylate solvent.

[0018] Furthermore, the linear carbonate solvent includes at least one of dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

[0019] Furthermore, the cyclic carbonate solvent includes at least one of ethylene carbonate, fluoroethylene carbonate and propylene carbonate.

[0020] Furthermore, the carboxylate solvent includes at least one of propyl acetate, ethyl acetate and propyl propionate.

[0021] In a second aspect, the present invention further provides a sodium ion battery comprising the electrolyte as described above.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The electrolyte of the present invention effectively solves the problems of transition metal dissolution and electrode corrosion caused by HF by adding additives, and realizes the construction of a complete, dense, highly stable, rigid and flexible positive electrode solid electrolyte membrane; wherein the fluorine atoms in the additives have a strong electron-withdrawing effect, and the in-situ formed NaF is introduced into the CEI membrane, which can improve the mechanical strength of the CEI membrane and enhance the stability of the CEI membrane; the alkaline electron donor Si-O bond can effectively complex HF, PF5 and trace water in the electrolyte to prevent corrosion of the positive electrode; the benzene ring structure can improve the flexibility and integrity of the positive electrode solid electrolyte interface membrane.

[0024] The electrolyte of the present invention is used in a sodium ion battery, which is beneficial to improving the cycle performance of the sodium ion battery, especially the cycle performance under high temperature and high pressure conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 The following are comparison curves of the room temperature cycle performance of sodium ion batteries prepared using the electrolytes of Examples 1 to 3 and Comparative Example 1, respectively.

[0027] Figure 2 The high temperature cycle performance comparison curves of the sodium ion batteries prepared by the electrolytes of Example 4 and Comparative Example 2 of the present invention are shown. DETAILED DESCRIPTION

[0028] The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0029] The following is a detailed description of an electrolyte and a sodium ion battery of the present invention.

[0030] In some embodiments of the present invention, an electrolyte is provided, including an organic solvent, a sodium salt, and an additive;

[0031] The additive includes at least one of the compounds having the structure shown below;

[0032] In the formula, R is selected from at least one of hydrogen, halogen, silane, substituted or unsubstituted C1-C6 alkyl, phenyl, substituted phenyl, amine, pyrrolyl, thienyl, furanyl, pyridyl, pyrazinyl and pyrimidyl.

[0033] The electrolyte of the present invention effectively solves the problems of transition metal dissolution and electrode corrosion caused by HF by adding the additive having the above structure, and can form a stable CEI film with high mechanical strength on the surface of the positive electrode, thereby facilitating the improvement of the cycle performance of the sodium ion battery, especially the cycle performance under high temperature and high pressure conditions.

[0034] The fluorine atoms in the additive of the present invention have a strong electron-withdrawing effect, and the in-situ formed NaF is introduced into the CEI film, which can improve the mechanical strength of the CEI film and enhance the stability of the CEI film.

[0035] The alkaline electron donor Si-O bond in the additive of the present invention can effectively complex HF, PF5 and trace water in the electrolyte to prevent corrosion of the positive electrode.

[0036] The benzene ring structure in the additive of the present invention can improve the flexibility and integrity of the positive electrode solid electrolyte interface film.

[0037] The synergistic effect of the fluorine, silicon and benzene functional groups in the additive of the present invention can realize the successful construction of a complete, dense, highly stable, rigid and flexible positive electrode solid electrolyte membrane.

[0038] In some embodiments of the present invention, the additive includes at least one of the compounds having structures shown in Formula (I) to Formula (VII);

[0039]

[0040] In some embodiments of the present invention, the mass of the additive accounts for 0.001% to 10% of the total mass of the electrolyte; typically but not limiting, for example, the mass of the additive accounts for 0.001%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% of the total mass of the electrolyte or a range of any two thereof; preferably, the mass of the additive accounts for 0.1% to 5% of the total mass of the electrolyte.

[0041] In some embodiments of the present invention, the sodium salt includes at least one of sodium hexafluorophosphate, sodium perchlorate, sodium hexafluoroarsenate, sodium p-toluenesulfonate, sodium tetrafluoroborate, sodium bis(trifluoromethylsulfonyl)imide and sodium bis(perfluoroethylsulfonyl)imide.

[0042] In some embodiments of the present invention, the concentration of sodium salt in the electrolyte is 0.5 to 3 mol / L; typically but not limitatively, for example, the concentration of sodium salt in the electrolyte can be 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L or a range consisting of any two of them.

[0043] In some embodiments of the present invention, the organic solvent includes at least one of a linear carbonate solvent, a cyclic carbonate solvent, and a carboxylate solvent.

[0044] In some embodiments of the present invention, the linear carbonate solvent includes at least one of dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

[0045] In some embodiments of the present invention, the cyclic carbonate solvent includes at least one of ethylene carbonate, fluoroethylene carbonate and propylene carbonate.

[0046] In some embodiments of the present invention, the carboxylate solvent includes at least one of propyl acetate, ethyl acetate and propyl propionate.

[0047] In some embodiments of the present invention, a method for preparing the above electrolyte is also provided, comprising the following steps:

[0048] After the organic solvent, sodium salt and additive are mixed evenly, an electrolyte is obtained.

[0049] In some embodiments of the present invention, a sodium ion battery is also provided, comprising the above-mentioned electrolyte.

[0050] The electrolyte of the present invention is used in a sodium ion battery, which is beneficial to improving the cycle performance of the sodium ion battery, especially the cycle performance under high temperature and high pressure conditions.

[0051] Example 1

[0052] The method for preparing the electrolyte provided in this embodiment comprises the following steps:

[0053] Ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a volume ratio of 1:1:1 are mixed evenly, and then sodium hexafluorophosphate is added and mixed evenly to obtain a mixed solution; in the mixed solution, the concentration of sodium hexafluorophosphate is 1 mol / L;

[0054] Adding an additive to the mixed solution to obtain an electrolyte; the mass of the additive accounts for 0.15% of the total mass of the electrolyte;

[0055] The structural formula of the additive is

[0056] Example 2

[0057] The method for preparing the electrolyte provided in this embodiment comprises the following steps:

[0058] Ethylene carbonate and dimethyl carbonate in a volume ratio of 1:1 are mixed evenly, and then sodium hexafluorophosphate is added and mixed evenly to obtain a mixed solution; in the mixed solution, the concentration of sodium hexafluorophosphate is 1 mol / L;

[0059] Adding an additive to the mixed solution to obtain an electrolyte; the mass of the additive accounts for 0.05% of the total mass of the electrolyte;

[0060] The structural formula of the additive is

[0061] Example 3

[0062] The method for preparing the electrolyte provided in this embodiment comprises the following steps:

[0063] Ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a volume ratio of 1:1:1 are mixed evenly, and then sodium hexafluorophosphate is added and mixed evenly to obtain a mixed solution; in the mixed solution, the concentration of sodium hexafluorophosphate is 1 mol / L;

[0064] Adding an additive to the mixed solution to obtain an electrolyte; the mass of the additive accounts for 0.2% of the total mass of the electrolyte;

[0065] The structural formula of the additive is

[0066] Example 4

[0067] The method for preparing the electrolyte provided in this embodiment comprises the following steps:

[0068] Diethyl carbonate, ethylene carbonate and dimethyl carbonate in a volume ratio of 1:1:1 are mixed evenly, and then sodium hexafluorophosphate is added and mixed evenly to obtain a mixed solution; in the mixed solution, the concentration of sodium hexafluorophosphate is 1 mol / L;

[0069] Adding an additive to the mixed solution to obtain an electrolyte; the mass of the additive accounts for 0.1% of the total mass of the electrolyte;

[0070] The structural formula of the additive is

[0071] Example 5

[0072] The method for preparing the electrolyte provided in this embodiment comprises the following steps:

[0073] Diethyl carbonate, ethylene carbonate and dimethyl carbonate in a volume ratio of 1:1:1 are mixed evenly, and then sodium hexafluorophosphate is added and mixed evenly to obtain a mixed solution; in the mixed solution, the concentration of sodium hexafluorophosphate is 1 mol / L;

[0074] Adding an additive to the mixed solution to obtain an electrolyte; the mass of the additive accounts for 0.2% of the total mass of the electrolyte;

[0075] The structural formula of the additive is

[0076] Example 6

[0077] The method for preparing the electrolyte provided in this embodiment comprises the following steps:

[0078] Diethyl carbonate, ethylene carbonate and dimethyl carbonate in a volume ratio of 1:1:1 are mixed evenly, and then sodium hexafluorophosphate is added and mixed evenly to obtain a mixed solution; in the mixed solution, the concentration of sodium hexafluorophosphate is 1 mol / L;

[0079] Adding an additive to the mixed solution to obtain an electrolyte; the mass of the additive accounts for 0.1% of the total mass of the electrolyte;

[0080] The structural formula of the additive is

[0081] Example 7

[0082] The method for preparing the electrolyte provided in this embodiment comprises the following steps:

[0083] Ethylene carbonate and dimethyl carbonate in a volume ratio of 1:1 are mixed evenly, and then sodium hexafluorophosphate is added and mixed evenly to obtain a mixed solution; in the mixed solution, the concentration of sodium hexafluorophosphate is 1 mol / L;

[0084] Adding an additive to the mixed solution to obtain an electrolyte; the mass of the additive accounts for 0.05% of the total mass of the electrolyte;

[0085] The structural formula of the additive is Comparative Example 1

[0086] The preparation method of the electrolyte provided in this comparative example comprises the following steps:

[0087] Ethylene carbonate and dimethyl carbonate are mixed evenly in a volume ratio of 1:1, and then sodium hexafluorophosphate is added and mixed evenly to obtain an electrolyte; in the electrolyte, the sodium hexafluorophosphate concentration is 1 mol / L.

[0088] Comparative Example 2

[0089] The preparation method of the electrolyte provided in this comparative example comprises the following steps:

[0090] Diethyl carbonate, ethylene carbonate and dimethyl carbonate in a volume ratio of 1:1:1 are mixed evenly, and then sodium hexafluorophosphate is added and mixed evenly to obtain an electrolyte; in the electrolyte, the sodium hexafluorophosphate concentration is 1 mol / L.

[0091] Test example

[0092] Sodium ion batteries (soft pack batteries) were prepared using the electrolytes of Examples 1 to 3 and Comparative Example 1, and then the room temperature cycle performance test was performed. The results are shown in Table 1. The room temperature cycle performance comparison curves of the sodium ion batteries prepared using the electrolytes of Examples 1 to 3 and Comparative Example 1 are shown in Table 1. Figure 1 shown.

[0093] The sodium ion battery uses Na2MnFe(CN)6 as the positive electrode, hard carbon as the negative electrode, and celgard2400 as the separator.

[0094] The method for testing the room temperature cycle performance of sodium ion batteries is as follows: the room temperature test temperature is 25°C, three cycles of activation at a rate of 0.2C at a voltage of 2.0-3.65V, and then 500 cycles of constant current charge and discharge at a rate of 1C; compare the battery's first coulombic efficiency, and capacity retention rate data after 100, 200 and 500 cycles.

[0095] Table 1

[0096]

[0097] The electrolytes of Examples 4 to 7 and Comparative Example 2 were used to prepare sodium ion batteries (soft pack batteries), and then high temperature cycle performance tests were performed. The results are shown in Table 2. The high temperature cycle performance comparison curves of the sodium ion batteries prepared using the electrolytes of Example 4 and Comparative Example 2 are shown in Table 2. Figure 2 shown.

[0098] The sodium ion battery uses Na2MnFe(CN)6 as the positive electrode, hard carbon as the negative electrode, and celgard2400 as the separator.

[0099] The method for testing the high-temperature cycle performance of sodium-ion batteries is as follows: the high-temperature cycle test temperature is 45°C, three cycles of activation at a rate of 0.2C at a voltage of 2.0-3.65V, and then 500 cycles of constant current charge and discharge at a rate of 1C; the battery's first coulombic efficiency, and capacity retention rate data after 100, 200 and 500 cycles are compared.

[0100] Table 2

[0101]

[0102] It can be seen from Table 1 and Table 2 that at room temperature, the various properties of the sodium ion batteries prepared by the electrolytes of Examples 1 to 3 are better than those of Comparative Example 1, and at a high temperature of 45°C, the various properties of the sodium ion batteries prepared by the electrolytes of Examples 4 to 7 are better than those of Comparative Example 2, which shows that in the electrolysis of the present invention, the fluorine- and silicon-containing additives effectively solve the problems of positive electrode corrosion and transition metal dissolution caused by HF, and can form a complete, stable, and rigid and flexible CEI film on the surface of the positive electrode, effectively improving the cycle performance of the sodium ion battery.

[0103] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An electrolyte, characterized in that: Including organic solvents, sodium salts and additives; The additive includes at least one of the compounds having the structure shown below; In the formula, R is selected from at least one of hydrogen, halogen, silane, substituted or unsubstituted C1-C6 alkyl, phenyl, substituted phenyl, amine, pyrrolyl, thienyl, furanyl, pyridyl, pyrazinyl and pyrimidyl.

2. The electrolyte according to claim 1, characterized in that The additive includes at least one of the compounds having structures shown in formula (I) to formula (VII); 3. The electrolyte according to claim 1, characterized in that The mass of the additive accounts for 0.001% to 10% of the total mass of the electrolyte.

4. The electrolyte according to claim 1, characterized in that The sodium salt includes at least one of sodium hexafluorophosphate, sodium perchlorate, sodium hexafluoroarsenate, sodium p-toluenesulfonate, sodium tetrafluoroborate, sodium bis(trifluoromethylsulfonyl)imide and sodium bis(perfluoroethylsulfonyl)imide.

5. The electrolyte according to claim 1, characterized in that In the electrolyte, the concentration of the sodium salt is 0.5 to 3 mol / L.

6. The electrolyte according to claim 1, characterized in that The organic solvent includes at least one of a linear carbonate solvent, a cyclic carbonate solvent and a carboxylate solvent.

7. The electrolyte according to claim 6, characterized in that The linear carbonate solvent includes at least one of dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

8. The electrolyte according to claim 6, characterized in that The cyclic carbonate solvent includes at least one of ethylene carbonate, fluoroethylene carbonate and propylene carbonate.

9. The electrolyte according to claim 6, characterized in that The carboxylate solvent includes at least one of propyl acetate, ethyl acetate and propyl propionate.

10. A sodium ion battery, characterized in that: The electrolyte comprises the electrolyte described in any one of claims 1 to 9.

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